#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>

int main()
{
    int num[5] = { 0 };
    int i = 0, sum = 0;

    while (scanf("%d", &num[i]) != EOF)
    {
        sum += num[i];
    }
    double average = sum / 5.0;
    printf("%.1lf\n", average);
    return 0;
}